Heretofore, various proposals have been made with respect to catalysts for gas phase catalytic oxidation of propylene with a molecular oxygen-containing gas to produce acrolein and acrylic acid, and catalysts for gas phase catalytic oxidation of isobutylene, tertiary butyl alcohol or methyl tertiary butyl ether with a molecular oxygen-containing gas to produce methacrolein and methacrylic acid.
These catalysts are, of course, required to be able to produce the desired corresponding unsaturated aldehyde and unsaturated carboxylic acid in good yield, but also required to have sufficiently high mechanical strength and durability durable for industrial use for a long period of time.
Heretofore, in order to improve the properties of the catalyst to be used for such a reaction, it has been proposed to control pores of the catalyst by using various organic compounds. As such examples, Patent Documents 1, 2 and 3, etc. are known. Such a method has a merit in that the pore size of a catalyst can relatively freely be changed by adding an organic compound having the type or grain size changed at the time of the production of the catalyst and removing the organic compound used by heat treatment. However, such a method has a problem that at the time of removal of the organic compound, sintering of the catalyst by combustion of the organic compound, or reduction of the catalyst by the organic compound takes place, whereby the activating treatment tends to be complicated, and reproducibility of the catalyst performance tends to be poor.
Further, Patent Document 4 proposes to use activated carbon at the time of producing a catalyst in order to improve the performance and mechanical strength of the catalyst. Namely, it is proposed that a mixture of the above-mentioned catalyst components is calcined, and activated carbon having a prescribed particle size is mixed to the obtained calcined product, followed by molding and heat treatment. However, also in this case, there is still a room for improvement with respect to the yield of the desired unsaturated aldehyde and unsaturated carboxylic acid.
Thus, a new process for producing a catalyst, whereby the catalyst performance can easily be improved or increased and is excellent in reproducibility, is desired.
Patent Document 1: JP-A-58-98143
Patent Document 2: JP-A-3-109946
Patent Document 3: JP-3278246
Patent Document 4: JP-3251641